Implantable medical elongated member including fixation elements along an interior surface

ABSTRACT

An implantable medical elongated member includes a first outer surface portion and a second outer surface portion extending around at least ten percent of an outer perimeter of the elongated member. A fixation element extends a distance from the first outer surface portion of the implantable medical elongated member. A longitudinally-extending section of the second outer surface portion proximate to a distal end of the elongated member is substantially devoid of any fixation elements that extend the distance from second outer surface portion.

TECHNICAL FIELD

The invention relates to medical device systems and, more particularly,to elongated members in medical device systems.

BACKGROUND

Electrical stimulation systems may be used to deliver electricalstimulation therapy to patients to treat a variety of symptoms orconditions such as chronic pain, tremor, Parkinson's disease, multiplesclerosis, spinal cord injury, cerebral palsy, amyotrophic lateralsclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders,gastroparesis, muscle stimulation (e.g., functional electricalstimulation (FES) of muscles) or obesity. An electrical stimulationsystem typically includes one or more implantable medical leads coupledto an electrical stimulator.

The implantable medical lead may be percutaneously or surgicallyimplanted in a patient on a temporary or permanent basis such that atleast one stimulation electrode is positioned proximate to a targetstimulation site. The target stimulation site may be, for example, anerve or other tissue site, such as a spinal cord, pelvic nerve,pudendal nerve, stomach, bladder, or within a brain or other organ of apatient, or within a muscle or muscle group of a patient. The one ormore electrodes located proximate to the target stimulation site maydeliver electrical stimulation therapy to the target stimulation site inthe form electrical signal s.

Electrical stimulation of a sacral nerve may eliminate or reduce somepelvic floor disorders by influencing the behavior of the relevantstructures, such as the bladder, sphincter and pelvic floor muscles.Pelvic floor disorders include urinary incontinence, urinaryurge/frequency, urinary retention, pelvic pain, bowel dysfunction, andmale and female sexual dysfunction. The organs involved in bladder,bowel, and sexual function receive much of their control via the second,third, and fourth sacral nerves, commonly referred to as S2, S3 and S4respectively. Thus, in order to deliver electrical stimulation to atleast one of the S2, S3, or S4 sacral nerves, an implantable medicallead is implanted proximate to the sacral nerve(s).

Electrical stimulation of a peripheral nerve, such as stimulation of anoccipital nerve, may be used to mask a patient's feeling of pain with atingling sensation, referred to as paresthesia. Occipital nerves, suchas a lesser occipital nerve, greater occipital nerve or third occipitalnerve, exit the spinal cord at the cervical region, extend upward andtoward the sides of the head, and pass through muscle and fascia to thescalp. Pain caused by an occipital nerve, e.g. occipital neuralgia, maybe treated by implanting a lead proximate to the occipital nerve todeliver stimulation therapy.

In many electrical stimulation applications, it is desirable for astimulation lead to resist migration following implantation. Forexample, it may be desirable for the electrodes disposed at a distal endof the implantable medical lead to remain proximate to a targetstimulation site in order to provide adequate and reliable stimulationof the target stimulation site. In some applications, it may also bedesirable for the electrodes to remain substantially fixed in order tomaintain a minimum distance between the electrode and a nerve in orderto help prevent inflammation to the nerve and in some cases, unintendednerve damage. Securing the implantable medical lead at the targetstimulation site may minimize lead migration.

SUMMARY

In general, the invention is directed toward an implantable medicalelongated member that includes one or more fixation elements along aninterior surface of the elongated member, as well as a method forimplanting the elongated member in a patient. The elongated member isconfigured to be coupled to a medical device to deliver a therapy fromthe medical device to target therapy delivery site in a patient. Thetherapy may be electrical stimulation, drug delivery, or both.

An “interior” surface of the elongated member is a portion of an outersurface of the elongated member that generally faces away from anepidermis layer of a patient (or a scalp of the patient, depending onthe particular application of the elongated member) when implanted insubcutaneous tissue of the patient. Accordingly, an “exterior” side ofthe elongated member generally faces toward the epidermis of the patientwhen the elongated member is implanted in subcutaneous tissue of apatient. The elongated member may be implanted so that the fixationelements face inward away from an integumentary layer of the patient(e.g., the epidermis, dermis, or scalp), rather than outward so as toavoid damage to the integumentary layer or irritation to the patientfrom engagement of a fixation member with the integumentary layer. Inone embodiment, the elongated member is fixed at one or more points thatare distributed about less than a full outer perimeter of the elongatedmember in order to minimize or eliminate points of stress between theone or more fixation elements and the epidermis or scalp of a patient.

In accordance with one embodiment of the invention, at least a sectionof the exterior surface of the elongated member near a distal end of theelongated member is devoid of any fixation elements in order to helpminimize or prevent stress points between the elongated member and anintegumentary layer of the patient. In other embodiments, the exteriorsurface includes fixation elements that are sized to minimize anyinterference with the epidermis or scalp of the patient.

In one embodiment, the elongated member is an implantable medical leadthat is coupled to an implantable or external electrical stimulator,which is configured to deliver electrical stimulation therapy to atarget stimulation site in a patient via the lead, and morespecifically, via at least one electrode disposed adjacent to a distalend of a lead body of the lead. The lead may be, for example, acylindrical lead or a paddle lead. In another embodiment, the elongatedmember is a catheter configured to deliver a fluid, such aspharmaceutical agents, insulin, pain relieving agents, gene therapyagents, or the like from an implantable or external fluid reservoirand/or pump to a target tissue site in a patient.

The fixation element may be any suitable fixation element that helpssubstantially fix a position of the elongated member to (e.g., at ornear) the target therapy delivery site, thereby reducing migration ofthe elongated member when the elongated member is implanted in apatient.

In one embodiment, the invention is directed to an apparatus comprisingan implantable medical elongated member configured to couple to amedical device to deliver a therapy from the medical device to a targettherapy delivery site in a patient. The elongated member extends betweena proximal end and a distal end and defines an outer surface comprisinga first outer surface portion, and a second outer surface portionextending around at least ten percent of an outer perimeter of theelongated member. The apparatus further comprises a fixation elementextending a distance from the first outer surface portion of theimplantable medical elongated member. A longitudinally-extending sectionof the second outer surface portion proximate to the distal end of theelongated member and extending around at least ten percent of the outerperimeter of the elongated member is substantially devoid of anyfixation elements that extend the distance from second outer surfaceportion.

In another embodiment, the invention is directed to a system including amedical device and an elongated member. The implantable medicalelongated member is configured to couple to the medical device todeliver a therapy from the medical device to a target therapy deliverysite in a patient. The elongated member extends between a proximal endand a distal end and defines an outer surface comprising a first outersurface portion, and a second outer surface portion extending around atleast ten percent of an outer perimeter of the elongated member. Theapparatus further comprises a fixation element extending a distance fromthe first outer surface portion of the implantable medical elongatedmember. A longitudinally-extending section of the second outer surfaceportion proximate to the distal end of the elongated member andextending around at least ten percent of the outer perimeter of theelongated member is devoid of any fixation elements that extend thedistance from second outer surface portion.

In yet another embodiment, the invention is directed toward animplantable medical lead comprising a lead body, one or more electrodescarried by the lead body, and one or more fixation elements extendingfrom an outer surface of the lead body. At least a circumferentialsub-section of the outer surface extending over at least ten degrees issubstantially devoid of the fixation elements.

In yet another embodiment, the invention is directed to method forimplanting an elongated member in a patient. The method comprisesintroducing the elongated member a patient. The elongated member extendsbetween a proximal end and a distal end and defines an outer surfacecomprising a first outer surface portion and a second outer surfaceportion extending around at least ten percent of an outer perimeter ofthe elongated member. The elongated member further comprises a fixationelement extending a distance from the first outer surface portion of theimplantable medical elongated member. A longitudinally-extending sectionof the second outer surface portion proximate to the distal end of theelongated member and extending around at least ten percent of the outerperimeter of the elongated member is substantially devoid of anyfixation elements that extend the distance from second outer surfaceportion. The method further comprises orienting the elongated member sothat the second outer surface portion faces a superficial direction andadvancing the elongated member through the introducer to a targettherapy delivery site to deploy the fixation member into tissue of thepatient, wherein the fixation element engages with surrounding tissue tosubstantially fix a position of the elongated member proximate to thetarget therapy delivery site.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the implantation of a therapy system, which includesan electrical stimulator coupled to an implantable medical lead, at alocation proximate to an occipital nerve.

FIG. 2 is a block diagram illustrating various components of theelectrical stimulator and implantable lead of the therapy system of FIG.1.

FIG. 3A is a perspective view of the implantable medical lead of FIG. 1implanted in subcutaneous tissue.

FIG. 3B is a schematic cross-sectional view of the implantable medicallead of FIGS. 1-3A.

FIG. 3C is a schematic cross-sectional view of the introducer shown inFIG. 1 taken along line 3C-3C in FIG. 1.

FIGS. 4A-4B are schematic cross-sectional views of alternate embodimentsof implantable medical leads including fixation elements along a firstouter surface portion of the lead body.

FIGS. 5A-8 illustrate alternate arrangements of fixation elements on alead body.

FIG. 9 is a perspective view of a lead including fixation elementsextending radially outward from a lead body at approximately 90° withrespect to a first outer surface portion of the lead body.

FIGS. 10A and 10B are a perspective view and schematic cross-sectionalview, respectively, of a lead including a fixation element extendingaround a first outer surface portion of a lead body.

FIG. 11 is a schematic cross-sectional view of a lead including afixation element extending around less than a full first outer surfaceportion of a lead body.

FIG. 12A is a side view of a paddle lead including fixation elementsalong a first outer surface portion.

FIG. 12B is a schematic cross-sectional view of the paddle lead shown inFIG. 12A.

FIGS. 13A and 13B are side views of alternate embodiments of a paddlelead including fixation elements along both the first outer surfaceportion and the second outer surface portion.

FIG. 14 is a flow diagram illustrating one example method for implantinga lead including fixation members along a first outer surface portion inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates to an implantable medical elongated memberincluding one or more fixation elements disposed about an outer surfaceof the elongated member in an arrangement that minimizes or eliminatespoints of stress between the fixation elements and an integumentarylayer (e.g., an epidermis layer, dermis or scalp) of a patient. Forexample, the elongated member may include fixation elements thatradially extend from less than a full outer circumference of a lead bodyor fixation elements disposed along one outer surface portion of theelongated member. Due to the arrangement of the fixation elements aboutthe outer surface of the elongated member, the elongated member may beimplanted so that the fixation elements do not interfere with theepidermis, dermis, or scalp of the patient. For example, the elongatedmember may be implanted such that the fixation elements may face awayfrom the epidermis, dermis, or scalp of the patient.

The elongated member is configured to be coupled to a medical device todeliver a therapy from the medical device to target tissue in a patient.Various embodiments of the elongated member may be applicable todifferent therapeutic applications. For example, the elongated membermay be a stimulation lead or a lead extension that is used to deliverelectrical stimulation to a target stimulation site and/or senseparameters (e.g., blood pressure, temperature or electrical activity) ofa patient. In another embodiment, the elongated member may be a catheterthat is placed to deliver a fluid, such as pharmaceutical agents,insulin, pain relieving agents, gene therapy agents or the like from afluid delivery device (e.g., a fluid reservoir and/or pump) to a targettissue site in a patient. The invention is applicable to anyconfiguration or type of implantable elongated member that is used todeliver therapy to a site in a patient. For purposes of illustration,however, the disclosure will refer to a neurostimulation lead.

FIG. 1 a schematic perspective view of a therapy system 10, whichincludes an electrical stimulator 12 coupled to implantable medical lead14. Lead 14 is aligned to be introduced into introducer needle 16, whichis positioned proximate to target stimulation site 18 of patient 20. Inparticular, lead 14 is aligned to be implanted and anchored or fixatedwith fixation elements proximate to target stimulation site 18 withinpatient 20 for stimulation of one or more occipital nerves. In theexample shown in FIG. 1, target stimulation site 18 is proximate to atleast one of lesser occipital nerve 22, greater occipital nerve 24 orthird occipital nerve 26. In alternate embodiments, lead 14 may bepositioned proximate to one or more other peripheral nerves proximate tooccipital nerves 22, 24, and 26 of patient 20, such as nerves branchingfrom occipital nerves 22, 24 or 26. In addition, therapy system 10 maybe used to provide stimulation therapy to any other suitable nerveswithin patient 20, such as, but not limited to, trigeminal nerves,branches of trigeminal nerves or nerves within a brain, stomach orspinal cord of patient 20.

In the embodiment shown in FIG. 1, electrical stimulator 12 is aneurostimulator that is either implantable or external. For example,neurostimulator 12 may be subcutaneously implanted in the body of apatient (e.g., in a chest cavity, lower back, lower abdomen, or buttocksof patient 20). Neurostimulator 12 provides a programmable stimulationsignal (e.g., in the form of electrical pulses or substantiallycontinuous-time signals) that is delivered to target stimulation site 18by implantable medical lead 14, and more particularly, via one or morestimulation electrodes 28 carried by lead 14. In some embodiments,neurostimulator 12 may be coupled to two or more leads, e.g., forbilateral or multi-lateral stimulation. Stimulation of occipital nerves22, 24, and 26 may help alleviate pain associated with, for example,chronic migraines, cervicogenic headaches, occipital neuralgia ortrigeminal neuralgia. Neurostimulator 12 may also be referred to as apulse generator. In some embodiments, lead 14 may also carry one or moresense electrodes to permit neurostimulator 12 to sense electricalsignals from target stimulation site 18.

Proximal end 14A of lead 14 may be both electrically and mechanicallycoupled to connector 13 of neurostimulator 12 either directly orindirectly (e.g., via a lead extension). In particular, conductorsdisposed within a lead body of lead 14 electrically connect stimulationelectrodes 28 (and sense electrodes, if present) located adjacent todistal end 14B of lead 14 to neurostimulator 12.

As described in further detail below, lead 14 further includes one ormore one fixation elements (not shown in FIG. 1) extending from aninterior portion of an outer surface of lead 14 to help substantiallyfix lead 14 proximate to target stimulation site 18. In the embodimentshown in FIG. 1, an interior portion of the outer surface of lead 14faces away from scalp 30 of patient 20. By including one or morefixation elements that face away from scalp 30, and includingsubstantially no fixation elements on a side facing scalp 30, thepossibility of a fixation element (which may protrude from lead 14)extending into or through scalp 30 is minimized or eliminated. At thesame time, however, the inward-facing fixation elements are effective inresisting displacement of lead 14, and particularly electrodes 28, fromthe stimulation site. In one embodiment, an exterior portion of theouter surface of lead (i.e., a portion that faces scalp 30 when lead 14is implanted in patient 20) is devoid of any fixation elements, whichmay contribute to the comfort of patient 20 and avoidance of tissueerosion or damage when lead 14 is implanted in patient 20.

In the application of therapy system 10 shown in FIG. 1, implantation oflead 14 may involve the subcutaneous placement of lead 14 transverselyacross one or more occipital nerves 22, 24, and/or 26 that are causingpatient 20 to experience pain. Where treating occipital neuralgia,patient 30 may be placed in a lateral position or in a prone positionduring implantation of lead 14.

In order to locate the specific occipital nerve causing pain, aclinician may palpate the area of pain. In addition, some embodiments, ascreening lead may be used prior to implanting lead 14 to developoptimal stimulation parameters (e.g., various electrode combinations,amplitude, pulse width or rate).

In one example method of implanting lead 14 proximate to one or moreoccipital nerves 22, 24, and/or 26, a vertical skin incision 33approximately two centimeters in length is made in the neck of patient20 lateral to the midline of the spine at the level of the C1 vertebra.Fluoroscopy may be used to identify the location of the C1 vertebra.Typically, local anesthetic is used during the implantation procedure.The length of vertical skin incision 33 may vary depending on theparticular patient. At this location, the patient's skin and muscle areseparated by a band of connective tissue referred to as fascia.Introducer needle 16, which may be a Tuohy needle, is introduced intothe subcutaneous tissue, superficial to the fascia and muscle layer butbelow the skin. In some embodiments, introducer needle 16 may bemanually curved by the clinician to conform to the contour of the bodyof patient 20 proximate to the peripheral nerve, and in the embodimentshown in FIG. 1, the clinician may conform introducer needle 16 to thecontour of the neck of patient 20.

Occipital nerves 22, 24, and 26 are located within the cervicalmusculature and overlying fascia, and as a result, introducer needle 16,and eventually lead 14, are inserted superior to occipital nerves 22,24, and 26. That is, in one embodiment, introducer needle 16 isintroduced into the fascia layer of patient 20 such that introducerneedle 16 is between the skin of patient 20 and the occipital nerve 22,24, and/or 26 to be stimulated.

Introducer needle 16 may be guided transversely from incision 33 acrossthe midline of the spine of patient 16. Fluoroscopic observation may aidthe clinician in identifying the trunk of the occipital nerve.

Once introducer needle 16 is fully inserted, a needle stylet may beremoved from the introducer needle, if introducer needle 16 includes astylet. Lead 14 may then be advanced through introducer needle 16 andpositioned to allow stimulation of the lesser occipital nerve 22,greater occipital nerve 24, third occipital nerve 26, and/or otherperipheral nerves proximate to an occipital nerve. The position of lead14 may be verified via fluoroscopy or another suitable technique. Inaddition, the clinician may confirm that the electrodes proximate todistal end 14A of lead 14 are properly placed with respect to theparticular occipital nerve. For example, the clinician may provideelectrical signals to the electrodes and patient 30 may provide feedbackrelating to the paresthesia coverage. Upon placement of lead 14,introducer needle 16 may be removed (either before or after confirmingthe placement of the electrodes). As described below, in one embodiment,upon removal of introducer needle 16, the one or more fixation elementsof lead 14 engage with surrounding tissue to substantially fix aposition of lead 14 proximate to target stimulation site 18. In anotherembodiment, the one or more fixation elements of lead 14 adhere tosurrounding tissue to substantially fix a position of lead 14.

Accurate lead placement may affect the success of occipital nervestimulation, as well as any other nerve stimulation application oftherapy system 10. If lead 14 is located too deep, i.e. anterior, in thesubcutaneous tissue, patient 20 may experience muscle contractions,grabbing sensations, or burning. Such problems may additionally occur iflead 14 migrates after implantation. Furthermore, due to the location ofimplanted lead 14 on the back of the neck of patient 20, lead 14 may besubjected to pulling and stretching that may increase the chances oflead migration. For these reasons, fixating lead 14 may be advantageous.

Although occipital nerve stimulation is shown in FIG. 1, therapy system10 is useful in other neurostimulation applications. In alternateapplications of lead 14, target stimulation site 18 may be a locationproximate to other nerves, organs, muscles, muscle groups or othertissue sites in patient 20, which may be selected based on, for example,a therapy program selected for a particular patient 20. For example,therapy system 10 may be used to deliver neurostimulation therapy to asacral nerve, a pudendal nerve, a perineal nerve or other areas of thenervous system, in which cases, lead 14 would be implanted andsubstantially fixed proximate to the respective nerve. As furtherexamples, lead 14 may be positioned for temporary or chronic spinal cordstimulation for the treatment of pain, for peripheral neuropathy orpost-operative pain mitigation, ilioinguinal nerve stimulation,intercostal nerve stimulation, gastric stimulation for the treatment ofgastric mobility disorders and obesity, muscle stimulation (e.g.,functional electrical stimulation (FES) of muscles), for mitigation ofother peripheral and localized pain (e.g., leg pain or back pain), orfor deep brain stimulation to treat movement disorders and otherneurological disorders. Accordingly, although patient 20 and targetstimulation site 18 of FIG. 1 are referenced throughout the remainder ofthe disclosure for purposes of illustration, a neurostimulation lead 14in accordance with the invention may be adapted for use in a variety ofelectrical stimulation applications.

Therapy system 10 may also include clinician programmer 32 and patientprogrammer 34. Clinician programmer 32 may be a handheld computingdevice that permits a clinician to program neurostimulation therapy forpatient 20, e.g., using input keys and a display. For example, usingclinician programmer 32, the clinician may specify neurostimulationparameters for use in delivery of neurostimulation therapy. Clinicianprogrammer 32 supports telemetry (e.g., radio frequency (RF) telemetry)with neurostimulator 12 to download neurostimulation parameters and,optionally, upload operational or physiological data stored byneurostimulator 12. In this manner, the clinician may periodicallyinterrogate neurostimulator 12 to evaluate efficacy and, if necessary,modify the stimulation parameters.

Like clinician programmer 32, patient programmer 34 may be a handheldcomputing device. Patient programmer 34 may also include a display andinput keys to allow patient 20 to interact with patient programmer 34and neurostimulator 12. In this manner, patient programmer 34 providespatient 20 with an interface for control of neurostimulation therapy byneurostimulator 12. For example, patient 20 may use patient programmer34 to start, stop or adjust neurostimulation therapy. In particular,patient programmer 34 may permit patient 20 to adjust stimulationparameters such as duration, amplitude, pulse width and pulse rate,within an adjustment range specified by the clinician via clinicianprogrammer 34, or select from a library of stored stimulation therapyprograms.

Neurostimulator 12, clinician programmer 32, and patient programmer 34may communicate via cables or a wireless communication, as shown inFIG. 1. Clinician programmer 32 and patient programmer 34 may, forexample, communicate via wireless communication with neurostimulator 12using RF telemetry techniques known in the art. Clinician programmer 32and patient programmer 34 also may communicate with each other using anyof a variety of local wireless communication techniques, such as RFcommunication according to the 802.11 or Bluetooth specification sets,infrared communication, e.g., according to the IrDA standard, or otherstandard or proprietary telemetry protocols.

FIG. 2 is a block diagram illustrating various components ofneurostimulator 12 and an implantable medical lead 14. Neurostimulator12 includes therapy delivery module 40, processor 42, memory 44,telemetry module 46, and power source 47. In some embodiments,neurostimulator 12 may also include a sensing circuit (not shown in FIG.2). Implantable medical lead 14 includes lead body 48 extending betweenproximal end 48A and distal end 48B. In the embodiment of FIG. 2, leadbody 48 is cylindrical and defines an outer surface including a firstportion 49A, which is facing away from the plane of the image of FIG. 2.The outer surface of lead body 48 further defines a second portion 49B(not shown in FIG. 2) that faces into the plane of the image of FIG. 2.In other embodiments, lead body 48 may be paddle-shaped (i.e., a“paddle” lead), in which case lead body 48 would define two opposingsurfaces, as shown in FIG. 11 with respect to lead 142.

Electrodes 28A, 28B, 28C, and 28D (collectively “electrodes 28”) aredisposed on lead body 48 adjacent to distal end 48B of lead body 48. Insome embodiments, electrodes 28 may be ring electrodes. In otherembodiments, electrodes 28 may be segmented or partial ring electrodes,each of which extends along an arc less than 360 degrees (e.g., 90-120degrees) around the circumference of lead body 48. The configuration,type, and number of electrodes 28 illustrated in FIG. 2 are merelyexemplary.

In embodiments in which lead 14 is a paddle lead, electrodes 28 mayextend along one side of lead body 48. Electrodes 28 extending around aportion of the circumference of lead body 48 or along one side of apaddle lead may be useful for providing an electrical stimulation fieldin a particular direction/targeting a particular therapy deliver site.For example, in the electrical stimulation application shown in FIG. 1,electrodes 28 may be disposed along lead body 48 such that theelectrodes face toward occipital nerves 22, 24, and/or 26, or otherwiseaway from scalp 30. This may be an efficient use of stimulation becauseelectrical stimulation of scalp 30 may not provide any or very minimaluseful therapy to patient 20. In addition, the use of segmented orpartial ring electrodes 28 may also reduce the overall power deliveredto electrodes 28 by neurostimulator 12 because of the efficient deliveryof stimulation to occipital nerves 22, 24, and/or 26 (or other targetstimulation site) by eliminating or minimizing the delivery ofstimulation to unwanted or unnecessary regions within patient 20.

In embodiments in which electrodes 28 extend around a portion of thecircumference of lead body 48 or along one side of a paddle lead, lead14 may include one or more orientation markers 45 proximate to proximalend 14A that indicate the relative location of electrodes 28.Orientation marker 45 may be a printed marking on lead body 48, anindentation in lead body 48, a radiographic marker, or another type ofmarker that is visible or otherwise detectable (e.g., detectable by aradiographic device) by a clinician. Orientation marker 45 may help aclinician properly orient lead 14 such that electrodes 28 face thedesired direction (e.g., toward occipital nerves 22, 24, and/or 26)within patient 20. For example, orientation marker 45 may also extendaround the same portion of the circumference of lead body 48 or alongthe side of the paddle lead as electrodes 28. In this way, orientationmarker 45 faces the same direction as electrodes, thus indicating theorientation of electrodes 28 to the clinician. When the clinicianimplants lead 14 in patient 20, orientation marker 45 may remain visibleto the clinician.

Neurostimulator 12 delivers stimulation therapy via electrodes 28 oflead 14. In particular, electrodes 28 are electrically coupled to atherapy delivery module 40 of neurostimulator 12 via conductors withinlead body 48. In one embodiment, an implantable signal generator orother stimulation circuitry within therapy delivery module 40 deliverselectrical signals (e.g., pulses or substantially continuous-timesignals, such as sinusoidal signals) to targets stimulation site 18(FIG. 1A) via at least some of electrodes 28 under the control of aprocessor 42. The implantable signal generator may be coupled to powersource 47. Power source 47 may take the form of a small, rechargeable ornon-rechargeable battery, or an inductive power interface thattranscutaneously receives inductively coupled energy. In the case of arechargeable battery, power source 47 similarly may include an inductivepower interface for transcutaneous transfer of recharge power.

The stimulation energy generated by therapy delivery module 40 may beformulated as neurostimulation energy, e.g., for treatment of any of avariety of neurological disorders, or disorders influenced by patientneurological response. The signal s may be delivered from therapydelivery module 40 to electrodes 28 via a switch matrix and conductorscarried by lead 14 and electrically coupled to respective electrodes 28.

Processor 42 may include a microprocessor, a controller, a DSP, an ASIC,an FPGA, discrete logic circuitry, or the like. Processor 42 controlsthe implantable signal generator within therapy delivery module 40 todeliver neurostimulation therapy according to selected stimulationparameters. Specifically, processor 42 controls therapy delivery module40 to deliver electrical signal s with selected amplitudes, pulse widths(if applicable), and rates specified by the programs. In addition,processor 42 may also control therapy delivery module 40 to deliver theneurostimulation signals via selected subsets of electrodes 28 withselected polarities. For example, electrodes 28 may be combined invarious bipolar or multi-polar combinations to deliver stimulationenergy to selected sites, such as nerve sites adjacent the spinalcolumn, pelvic floor nerve sites, or cranial nerve sites.

Processor 42 may also control therapy delivery module 40 to deliver eachstimulation signal according to a different program, therebyinterleaving programs to simultaneously treat different symptoms orprovide a combined therapeutic effect. For example, in addition totreatment of one symptom such as sexual dysfunction, neurostimulator 12may be configured to deliver neurostimulation therapy to treat othersymptoms such as pain or incontinence.

Memory 44 of neurostimulator 12 may include any volatile or non-volatilemedia, such as a RAM, ROM, NVRAM, EEPROM, flash memory, and the like. Insome embodiments, memory 44 of neurostimulator 12 may store multiplesets of stimulation parameters that are available to be selected bypatient 20 via patient programmer 34 (FIG. 1) or a clinician viaclinician programmer 32 (FIG. 1) for delivery of neurostimulationtherapy. For example, memory 44 may store stimulation parameterstransmitted by clinician programmer 32 (FIG. 1). Memory 44 also storesprogram instructions that, when executed by processor 42, causeneurostimulator 12 to deliver neurostimulation therapy. Accordingly,computer-readable media storing instructions may be provided to causeprocessor 42 to provide functionality as described herein.

In particular, processor 42 controls telemetry module 46 to exchangeinformation with an external programmer, such as clinician programmer 32and/or patient programmer 34 (FIG. 1), by wireless telemetry. Inaddition, in some embodiments, telemetry module 46 supports wirelesscommunication with one or more wireless sensors that sense physiologicalsignals and transmit the signals to neurostimulator 12.

As previously discussed, migration of lead 14 following implantation maybe undesirable, and may have detrimental effects on the quality oftherapy delivered to a patient 20. For example, with respect to theoccipital nerve stimulation application shown in FIG. 1, migration oflead 14 may cause displacement of electrodes 28 carried adjacent todistal end 14B of lead 14 with respect to target stimulation site 18. Insuch a situation, the electrodes may not be properly positioned todeliver therapy to target stimulation site 18, resulting in reducedelectrical coupling, and possibly undermining therapeutic efficacy ofthe neurostimulation therapy from system 10.

Substantially fixing lead 14 to surrounding tissue may help prevent lead14 from migrating from target stimulation site 18 followingimplantation, which may ultimately help avoid harmful effects that mayresult from a migrating lead 14. However, while it may be desirable tofix lead 14 such that electrodes 28 remain proximate to targetstimulation site 18 (FIG. 1), in some situations, it may also bedesirable to minimize discomfort to patient 20 from lead 14. Forexample, when lead 14 is implanted in a dermis or subcutaneous tissue ofpatient 20 (FIG. 1), such as in the occipital nerve stimulationapplication shown in FIG. 1, patient 20 may be more aware of lead 14 dueto the location of lead 14 near an epidermis, scalp 30 or anotherintegumentary layer of patient 20.

To that end, lead 14 includes fixation elements 50, 52, and 54 (notshown in FIG. 3A) along a first portion 49A of outer surface 49 of leadbody 48 to minimize migration of lead 14 and substantially fix aposition of electrodes 28 proximate to target stimulation site 18. Whenlead 14 is implanted proximate to target stimulation site 18, lead body48 may be oriented such that first portion 49A (“first outer surfaceportion”) of outer surface 49 generally faces away from the scalp 30 ofpatient and in an inward, deep direction and a majority of secondportion 49B (“second outer surface portion”) (shown in FIG. 3B) facesoutward in a superficial direction. In this way, first portion 49A ofouter surface 49 may also be referred to as an “interior surface” oflead body 48 and second portion 49B may also be referred to as an“exterior surface” of lead body 48. During implantation, the caregiverwill take note of the interior and exterior surfaces 49A, 49B of leadbody 48 and appropriately position lead 14 so that the interior andexterior surfaces face inward and outward, respectively.

Fixation elements 50, 52, and 54 engage with surrounding tissue attarget stimulation site 18 to fix a position of lead 14. When lead 14 isimplanted in patient 20 such that first outer surface portion 49A oflead body 48 faces away from scalp 30 (or another integumentary layer)of patient 20, fixation elements 50 and 54 extend substantially parallelto scalp 30 and fixation element 52 extends away from scalp 30. In theembodiment of lead 14 shown in FIG. 2, second portion 49B of outersurface 49 of lead body 48 is devoid of any fixation elements. As aresult, lead 14 does not include any fixation elements that may extendinto scalp 30, and possibly protrude through scalp 30, thereby resultingin an implantable medical lead 14 that is more comfortable to patient 20and reduces the possibility of erosion or damage to subcutaneous tissue.

Although lead 14 includes three fixation elements 50, 52, and 54 in theembodiment shown in FIG. 2, lead 14 may include any suitable number offixation elements 50, 52, and 54. Furthermore, fixation elements 50, 52,and 54 need not be protrusions that extend from lead 14. Fixationelements 50, 52, and 54 may be any suitable actively or passivelydeployed fixation element that helps prevent migration of lead 14 whenlead 14 is implanted in patient 20, such as, but not limited to, one ormore tines, barbs, hooks, wire-like elements, adhesives (e.g., surgicaladhesives), balloon-like fixation elements, pinning fixation elements,collapsible or expandable fixation structures, and so forth. Fixationelements 50, 52, and 54 may be composed of any suitable biocompatiblematerial, including, but not limited to, polymers, titanium, stainlesssteel, Nitinol, other shape memory materials, hydrogel or combinationsthereof.

Fixation elements 50, 52, and 54 may be any suitable size, which maydepend on the particular application of lead 14. In particular, it maybe desirable to select the size of or otherwise configure fixationelements 50, 52, and 54 to fix lead 14 to a particular region of thepatient proximate to the target stimulation site (e.g., a peripheralnerve stimulation site), which may involve selecting the size offixation elements 50, 52, and 54 to accommodate the specific anatomicalconfiguration of a region of the patient proximate to the peripheralnerve.

Furthermore, fixation elements 50, 54, and 54 may not be attacheddirectly to lead 14, but may be carried by another apparatus that isattached to the elongated member, such as a sleeve or mounting band. Anexample of a mounting band is described in commonly-assigned U.S. Pat.No. 6,999,819, entitled “IMPLANTABLE MEDICAL ELECTRICAL STIMULATION LEADFIXATION METHOD AND APPARATUS” and issued on Feb. 14, 2006, which ishereby incorporated by reference in its entirety.

Examples of suitable hydrogel fixation elements are described incommonly assigned U.S. Patent Application Publication No. 2006/0095077,entitled “EXPANDABLE FIXATION STRUCTURES and filed on Oct. 29, 2004,U.S. Patent Application Publication No. 2006/0095078, entitled“EXPANDABLE FIXATION MECHANISM” and filed on Oct. 29, 2004, and U.S.Patent Application Publication No. 2008/0103576 by Martin T. Gerber,entitled “IMPLANTABLE MEDICAL ELONGATED MEMBER INCLUDING EXPANDABLEFIXATION MEMBER” and filed on the same date as the present disclosure.

Other suitable fixation elements may include wire-like fixation elementsas described in commonly assigned U.S. Patent Application PublicationNo. 2005/0096718, entitled “IMPLANTABLE STIMULATION LEAD WITH FIXATIONMECHANISM” and filed on Oct. 31, 2003 and commonly-assigned U.S. PatentApplication Publication No. 2008/0103575 by Martin T. Gerber, entitled“IMPLANTABLE STIMULATION LEAD INCLUDING WIRE-LIKE FIXATION ELEMENTS” andfiled on the same date as the present disclosure. An example of tinefixation elements is described in U.S. Pat. No. 6,999,819, entitled“IMPLANTABLE MEDICAL ELECTRICAL STIMULATION LEAD FIXATION METHOD ANDAPPARATUS” and filed on Nov. 9, 2001.

An example of a suitable lead including a tissue-receiving cavity isdescribed in commonly-assigned U.S. Patent Application Publication No.2008/0103577 by Martin T. Gerber, entitled “IMPLANTABLE MEDICALELONGATED MEMBER INCLUDING A TISSUE RECEIVING CAVITY” and filed on thesame date as the present disclosure. An example of a suitable in situformed fixation element is described in commonly-assigned U.S. PatentApplication Publication No. 2008/0103578 by Martin F. Gerber, entitled“IMPLANTABLE MEDICAL ELONGATED MEMBER WITH IN SITU FORMED FIXATIONELEMENT” and filed on the same date as the present disclosure. Anexample of suitable balloon-like fixation elements are described incommonly-assigned U.S. Patent Application Publication No. 2008/0103575by Martin T. Gerber, entitled, “IMPLANTABLE STIMULATION LEAD INCLUDINGBALLOON FIXATION ELEMENT” and filed on the same date as the presentdisclosure.

Each of the aforementioned patents and patent applications relating tosuitable fixation elements are herein incorporated by reference in theirentirety.

FIG. 3A illustrates a schematic cross-sectional view of skin 61 ofpatient 20, which includes epidermis 62, dermis 64, and subcutaneoustissue 66, as well as a portion of a nerve 68. FIG. 3A further shows aperspective view of implantable medical lead 14 of FIGS. 1 and 2implanted in a subcutaneous tissue 66 proximate to nerve 68. FIG. 3Billustrates a schematic cross-sectional view of lead 14 taken along line3B-3B in FIG. 3A.

Distal end 48B of lead body 48 is shown in FIG. 3A. Proximal end 48A oflead body 48, which contains contacts (not shown in FIGS. 3A and 3B) toelectrically couple lead 14 (and in particular, electrodes 28) to a leadextension or a neurostimulator (e.g., neurostimulator 12 in FIG. 1).Skin 61 and nerve 68 are general representations of a region of patient20 and are shown to aid in the description of the invention, and thus,are not necessarily specific to a specific nerve of patient 20, nordrawn to any particular scale.

If neurostimulator 12 (FIGS. 1 and 2) is implanted in patient 20, theentire length of lead 14 is typically implanted in patient 20. On theother hand, if neurostimulator 12 is external, lead 14 may be partiallyimplanted within patient 20 and lead 14 (or a lead extension to whichproximal end 14A (shown in FIG. 1) is coupled) may extend throughepidermis layer 62 via a percutaneous port.

As previously discussed, lead body 48 defines outer surface 49, whichincludes first (“interior”) outer surface portion 49A and second(“exterior”) outer surface portion 49B, which are demarcated by line 69in FIG. 3A. In general, first outer surface portion 49A and second outersurface portion 49B do not overlap and have center points 70 and 72 thatare generally opposite each other. Center points 70 and 72 are shown inFIG. 3B and referred to herein as reference points to aid in thedescription of the invention. Fixation elements 50, 52, and 54 (shown inFIG. 3B) are distributed about less than a full outer perimeter of leadbody 48 because first outer surface portion 49A extends around less thana full outer perimeter of lead body 48. The outer perimeter of lead body48 is the outer circumference of lead body 48. In embodiments in which alead includes a noncircular cross-section, the outer perimeter of thelead body is defined by the outermost edge of a cross-section of thelead body.

In the embodiment shown in FIG. 3A, first outer surface portion 49A hasa larger size (i.e. measured in terms of surface area) than second outersurface portion 49B. In particular, in the embodiment shown in FIGS.3A-B, second outer surface portion 49B extends around less than or equalto about 50 percent (%) of the outer perimeter of lead body 48. In oneembodiment, second outer surface portion 49B extends around at least 10%of the outer perimeter of lead body 48, while second outer surfaceportion 49A extends around about 50% to about 90% of the outer perimeterof lead body 48. In the embodiment shown in FIGS. 3A-B, first outersurface portion 49A extends around approximately 75% of the outerperimeter of lead body 48. Therefore, fixation elements 50, 52, and 54are distributed about approximately 75% of the outer perimeter of leadbody 48. In some embodiments, first and second portions 49A and 49B maybe the same size. For example, demarcation line 69 may extend through acenter of lead body 48, such that first and second outer surfaceportions 49A and 49B each define a half of lead body 48. Alternatively,demarcation line 69 may be moved toward center point 70 of first portion49A to define a second portion 49B that is a greater (i.e., has agreater surface area) than first portion 49A.

In embodiments in which lead body 48 has a circular cross-section, thepercentages given above can be translated to a percentage of a circle.For example, in the embodiment shown in FIGS. 3A-B, first outer surfaceportion 49A extends around approximately 75% of the outer perimeter oflead body 48, or alternatively, extends over about 270°.

Regardless of the respective sizes of first and second outer surfaceportions 49A and 49B, lead 14 may be oriented and implanted in patientsuch that first outer surface portion 49A (particularly center point 70)generally faces a deep direction 67A (i.e., faces away from epidermis62), while a majority of second outer surface portion 49B (particularlycenter point 72) faces a superficial direction 67B (i.e., faces towardepidermis 62). Of course, due to the cylindrical shape of lead body 48in the example of FIGS. 3A and 3B, at least some of first outer surfaceportion 49A neither faces toward nor away from epidermis 62, but ratherfaces a direction 63 (shown in FIG. 3B) that is generally parallel toepidermis 62. Only a small percentage of second outer surface portion49B faces direction 63, and thus, it can be said that the “majority” ofsecond outer surface portion 49B faces a superficial direction.

Lead 14 may include a visible marker 65 (shown in FIG. 2 in phantom) onthe proximal end 48A of lead body 48. Visible marker 65 may provide areference point for a clinician during implantation of lead 14 inpatient 20. For example, the clinician may use visible marker 65 toorient lead 14 such that first outer surface portion 49A faces a deepdirection when lead 14 is implanted in patient 20. Visible marker 65 maybe a printed marking on lead body 48, an indentation in lead body 48, aradiographic marker, or another type of marker that is visible orotherwise detectable (e.g., detectable by a radiographic device) by aclinician. In FIG. 2, visible marker 65 is shown in phantom becausevisible marker 65 is located on second outer surface portion 49B of leadbody 48, which is facing into the plane of the image of FIG. 2.Alternatively, visible marker 65 may be on first outer surface portion49A. In other embodiments, visible marker 65 may be any suitableconfiguration (e.g., another shape, size, etc.).

In addition to or instead of visible marker 65, introducer 16 (FIG. 1)may have orientation marks to properly orient fixation elements 50, 52,and 54 of lead 14 with respect to epidermis 62 of patient 20. Forexample, proximal end 16A of introducer 16 may include printed markingsfor aligning with visible marker 65 of lead 14 to orient lead 14 suchthat first outer surface portion 49A faces away from epidermis 62 whenlead 14 is implanted in patient 20. In some embodiments, visible marker65 and orientation marker 45 may overlap and may effectively be a singlemarker.

FIG. 3C is a schematic cross-sectional view of introducer 16 taken alongline 3C-3C in FIG. 1. In embodiments in which fixation elements 50, 52,and 54 protrude from lead body 48 during an implantation procedure,introducer 16 may be keyed to receive lead 14 in a certain orientation.In the embodiment shown in FIG. 3C, introducer 16 defines lumen 79 forreceiving lead body 48, where lumen 79 defines channels 80A-C that aresized and otherwise configured to receive fixation elements 50, 52, and54, respectively, so that lead 14 may be introduced into introducer 16in a limited number of orientations. In this way, once introducer 16 isproperly oriented with respect to epidermis 62 of patient, introducer 16may be used to force proper orientation of lead 14 with respect toepidermis 62. Introducer 16 may be properly oriented with respect toepidermis 62 via any suitable means, such as, for example, visible orradiographic marker 81 on introducer 16. For example, when the clinicianis introducing introducer 16 into patient 20, the clinician may orientintroducer 16 such that visible or radiographic marker 81 is facing theclinician or facing a particular direction in order to properly orientchannels 80A-C with respect to epidermis 62. In addition, channels 80A-Cdefined by lumen 79 of introducer 16 may help minimize the overalldiameter of introducer 16, which may help minimize the invasiveness ofan implantation procedure.

In addition to or instead of visible marker 65 on lead body 48 ororienting features of introducer 16, a keyed stylet may be used to guidelead 14 into an orientation that results in fixation elements 50, 52,and 54 facing away from epidermis 62. For example, just as introducer 16is shown in FIG. 3C to be configured to receive lead 14 in oneorientation, a stylet may be keyed to receive lead 14 in oneorientation.

At least a longitudinally-extending section (i.e., extending in thedirection between proximal end 48A and distal end 48B of lead body 48)of second outer surface portion 49B near electrodes 28 is devoid of anyfixation elements or of any fixation elements that may extend intoepidermis layer 62 when lead 14 is implanted in subcutaneous tissue 66.For example, in the embodiment shown in FIG. 3A, the entire second outersurface portion 49B is devoid of any fixation elements. However, inother embodiments, second outer surface portion 49B may include fixationelements sized to engage with subcutaneous tissue 66, but not epidermis62 or dermis 64, or fixation elements to engage with dermis 64, but notepidermis 62. In another embodiment, a portion of second outer surfaceportion 49B other than the portion proximate to electrodes 28 mayinclude fixation members that are the same size or greater than fixationelements 50, 52, and 54.

Fixation elements 50, 52, and 54 are angled toward proximal end 48A oflead body 48, which may help distal end 48B of lead body 48 resist thepulling force from proximal end 48A. However, in some applications, itmay also be desirable for lead 14 to resist pulling forces from distalend 48B. Accordingly, the invention contemplates configurations offixation elements 50, 52, and 54 that are angled both toward and awayfrom proximal end 48A of lead body 48 (e.g., as shown in FIG. 8).

Fixation elements 50, 52, and 54 radially extend from lead body 48 at anacute angle with respect to first portion 49A. However, in otherembodiments, fixation elements 50, 52, and 54 radially extend from leadbody 48 at a 90° angle (e.g., as shown with respect to fixation elements126, 128, and 130 in FIG. 9). Extending from lead body 48 at an acuteangle enables fixation elements 50, 52, and 54 to engage withsurrounding tissue to prevent both axial and radial movement of leadbody 48.

FIG. 3B is a schematic cross-sectional view of lead 14 taken along line3B-3B in FIG. 3A. Lead body 48 carries a plurality of conductors 74(shown in FIG. 3B as a single conductive center of lead body 48 forclarity of illustration) for electrically coupling electrodes 28 (FIG.3A) to therapy delivery module 40 of neurostimulator 12 (FIG. 2).Typically, a separate conductor electrically couples each electrode28A-D to therapy delivery module 40. Separate conductors permitindependent selection of individual electrodes 28A-D. Furthermore, eachof the conductors electrically coupled to separate electrodes 28A-D areelectrically insulated from each other. Insulating layer 76 surroundsconductors 74 in order to electrically insulate conductors 74 fromsubcutaneous tissue 66 when lead 14 is implanted in patient 20 and tohelp protect a clinician who may be handling lead 14 from shock.

As previously described, each of fixation elements 50, 52 or 54 may bedirectly coupled to lead body 48, as shown in FIG. 3B, or indirectlycoupled to lead body 48 (e.g., carried by a fixation sleeve). In theembodiment shown in FIG. 3B, fixation elements 50, 52 or 54 are eachattached to lead body 48 with an adhesive. For example, adhesive 78 isdisposed between fixation element 54 and lead body 48.

As FIGS. 3A and 3B illustrate, when lead 14 is implanted in subcutaneoustissue 66, fixation elements 50 and 54 extend from lead body 48substantially parallel to epidermis layer 62, while fixation element 52extends away from epidermis layer 62. Implanting lead 14 withinsubcutaneous tissue 66 such that one or more fixation elements 50, 52 or54 extended through dermis layer 64 or even epidermis layer 66 mayincrease discomfort to patient 20. In addition, one or more fixationelements 50, 52 or 54 may be visible (e.g., a protrusion may be seenprotruding into epidermis 62). Discomfort to patient 20 may beattributable to the one or more fixation elements 50, 52 or 54 causingstress points at the interface between the one or more fixation elements50, 52 or 54 and dermis layer 64, or even epidermis layer 62. Inaddition, fixation elements 50, 52 or 54 may rub against dermis layer 64and/or even epidermis layer 62, which may lead to erosion of andpossible damage to dermis layer 64 and/or epidermis layer 62. Asdiscussed, in the embodiment of lead 14 shown in FIGS. 3A-3B, secondouter surface portion 49B is devoid of fixation elements. As a result,second outer surface portion 49B provides a relatively smooth surfacefor interfacing with epidermis layer 62 or dermis layer 64. Thus, insome applications, such as when lead 14 is implanted in subcutaneoustissue 66, it may be desirable for lead 14 to be implanted in a specificorientation.

In some embodiments, second outer surface portion 49B may includestructural fixation elements that also engage with surrounding tissue toprevent migration of lead 14. However, these fixation elements do notextend as far from second outer surface portion 49B as fixation elements50, 52 or 54 extend from first portion 49A in order to minimize theextent to which the fixation elements on second portion 49B engage withepidermis layer 62 or dermis layer 64. FIG. 4A is a schematiccross-sectional view of lead 55 including fixation element 56 extendingfrom second outer surface portion 49B of lead body 48. As FIG. 4Aillustrates, fixation element 56 is relatively small compared tofixation elements 50, 52, and 54. Fixation element 56 does not extend asfar from lead body 48 as fixation elements 50, 52, and 54. Inparticular, in the embodiment shown in FIG. 4A, fixation element 56extends a distance A from outer surface 49 of lead body 48, whilefixation element 52 (as well as fixation elements 50 and 54) extend adistance B from outer surface 49 of lead body 48. Distance B of fixationelement 56 may be selected such that fixation element 56 engages withsubcutaneous tissue 66, rather than epidermis layer 62 or dermis layer64, when lead 55 is implanted in subcutaneous tissue 66 of patient 20and oriented such that first outer surface portion 49A faces away fromepidermis layer 66.

Also shown in FIG. 4A are lines 57A and 57B, which are shown todemonstrate that lead body 48 defines four quadrants 58A-D. Rather thandescribing the arrangement of fixation elements 50, 52, 54, and 56 aboutlead body 48 with respect to first and second outer surface portions 49Aand 49B (FIG. 3B), respectively, the arrangement of fixation elements50, 52, 54, and 56 may also be described with respect to quadrants 58A-Dof lead body 48. In the embodiment of lead 55 shown in FIG. 4A, fixationelement 50 extends from first quadrant 58A of lead body 48, fixationelement 52 extends from second quadrant 58B, third fixation element 54extends from third quadrant 58C, and fixation element 56 extends fromfourth quadrant 58D. Fixation element 56 extending from fourth quadranthas a smaller cross-sectional profile than fixation elements 50, 52, and54.

Lead body 48 also defines quadrants 58A-D in each of the schematiccross-sectional views shown in FIGS. 3B, 4B, 5B, 6B, 10B, and 11.However, for clarity of illustration and description, quadrants are notlabeled in FIGS. 3B, 4B, 5B, 6B, 10B, and 11. Each of the leads shown inFIGS. 3B, 4B, 5B, 6B, 10B, and 11 may be described with respect toquadrants 58A-D. For example, lead 14 shown in FIG. 3B includes fixationelement 50 extends from first quadrant 58A of lead body 48, fixationelement 52 extends from second quadrant 58B, and third fixation element54 extends from third quadrant 58C, while fourth quadrant 58D is devoidof any fixation elements.

In yet another embodiment, second outer surface portion 49B may includea non-structural fixation element, such as a surgical adhesive. FIG. 4Bis a schematic cross-sectional view of lead 58 including adhesive layer59 along second outer surface portion 49B of lead body 48, and fixationelements 51, 52, and 54 along first outer surface portion 49A. As FIG.4B illustrates, adhesive layer 59 does not protrude from second portion49B of adhesive layer to the extend fixation elements 50, 52, and 54protrude from first portion 49A. In another embodiment, an adhesive maybe embedded in second portion 49B of lead body 48, rather than being aseparate adhesive layer 59. Regardless of the type of fixation element,if any, carried by second outer surface portion 49B, it is desirable tominimize the extent to which the fixation element along second outersurface portion 49B engages with and protrudes into-epidermis layer 62or dermis layer 64 in order to increase the comfort to patient 20.

Adhesive layer 59 may be, for example, surgical adhesive elementsdisposed on or embedded with second outer surface portion 49B of leadbody 48. Examples of suitable adhesive elements are discussed incommonly assigned U.S. Patent Application Publication No. 2008/0103579by Martin T. Gerber, entitled “IMPLANTABLE MEDICAL ELONGATED MEMBER WITHADHESIVE ELEMENTS” and filed on the same date as the present disclosure,which is hereby incorporated by reference in its entirety. The adhesiveproperties of adhesive layer 59 may be activated by any suitable means,including exposure to fluids, a certain temperature, or by activatingagents. For example, adhesive layer 59 may be separated from surroundingtissue by a sheath until lead 14 reaches a targets stimulation site, atwhich time a clinician may withdraw the sheath to expose adhesive layer59 to surrounding tissue, which may activate adhesive layer 59 viamoisture, temperature or otherwise.

Fixation element 51 of lead 58 is disposed on first outer surfaceportion 49A, but extends in a superficial direction toward epidermis 62when lead 58 is implanted in patient such that first outer surfaceportion 49A faces a deep direction. Although fixation element 51 extendstoward epidermis 62, fixation element 51 does not contact epidermis 62because of its placement on first outer surface portion 49A. Inparticular, fixation element 51 does not extend as far demarcation line69 separating first and second outer surface portions 49A and 49B,respectively.

While lead 14 includes three fixation elements 50, 52, and 54 spacedabout 90° with respect to each other about lead body 48, andparticularly, on first outer surface portion 49A, in other embodiments,a lead may include any suitable number of fixation elements in anysuitable arrangement about the lead body. These and other embodiments ofleads including alternate numbers and/or arrangements of fixationelements are shown in FIGS. 5A-13B and described in reference thereto.For clarity of description, like numbered reference numbers designatesubstantially similar elements throughout FIGS. 2-12. In FIGS. 1-13B,the components of the leads, as well as any other components that may beillustrated, are not necessarily drawn to scale. For example, each ofthe hydrogel fixation members 50, 52, and 54 shown in FIGS. 2-4B are notnecessarily drawn in correct proportion to the length or diameter oflead body 48.

FIGS. 5A and 5B are a perspective view and schematic cross-sectionalview, respectively, of lead 82, which includes fixation elements 83, 84,and 86 disposed between proximal end 48A and electrodes 28 for fixinglead 82 proximate to target stimulation site 18. As previouslydescribed, proximal end 48A of lead body typically includes contacts(not shown in FIG. 5A), for electrically connecting electrodes 28 oflead 82 with a neurostimulator (e.g., neurostimulator 12 in FIG. 1A), alead extension or other medical device. Fixation elements 83, 84, and 86are coupled to first outer surface portion 49A of outer surface 49 oflead body 48. In FIG. 5A, first outer surface portion 49A is shown,while second outer surface portion 49B faces into the plane of the imageof FIG. 5A. In FIG. 5B, line 69 indicates the demarcation between firstouter surface portion 49A and second outer surface portion 49B.

As FIG. 5B illustrates, fixation elements 83 and 84 are spaced aboutangle J with respect to each other about the outer perimeter of leadbody 48, while fixation elements 84 and 86 are spaced about angle K withrespect to each other. Angles J and K may, but need not be equal. Incontrast to fixation elements 50, 52, and 54 of lead 14 (FIGS. 2-4B),fixation elements 83, 84, and 86 are spaced less than about 90° withrespect to each other about first portion 49A of lead body 48. Forexample, angles J and K may each be about 45°. As a result of thearrangement of fixation elements 83, 84, and 86 about first outersurface portion 49A of lead body 48, when lead 82 is implanted insubcutaneous tissue 66 (FIG. 3A), fixation elements 83, 84, and 86extend away from epidermis layer 62. Thus, neither fixation element 83,84 or 86 radially extend from first portion 49A lead body 48 in adirection that results in fixation element 83, 84 or 86 that aresubstantially parallel to epidermis layer 62, as with fixation elements50 and 54 of lead 14 (FIGS. 2-3B).

First outer surface portion 49A of the lead body 48 of each of leads 14and 82 both include one set of fixation elements (i.e., a group offixation elements that substantially share an axial position withrespect to lead body 48) located proximal to electrodes 28. In otherembodiments, a lead may include more than one set of fixation elements,and the fixation elements may be otherwise arranged, such as betweenelectrodes 28, distal to electrodes 28, or combinations thereof.Examples of these embodiments are shown in FIGS. 6A-8.

FIGS. 6A and 6B are a perspective view and schematic cross-sectionalview of lead 90, which includes two sets 92 and 94 of fixation elementson first outer surface portion 49A that are axially displaced from eachother with respect to lead body 48. First set 92 include fixationelements 95-97, and second set 94 includes fixation elements 98-102. Asshown in FIG. 6B, in the cross-sectional view of lead 90, the fixationelements 95-102 do not overlap. Thus, fixation elements 95-97 of firstset 92 each have different radial locations about first outer surfaceportion 49A than fixation elements 98-102 of second set 94. Accordingly,fixation elements 95-102 each extend from first outer surface portion49A of lead body 48 in different radial directions.

First and second sets 92 and 94 of fixation elements are shown proximateto electrode 50. However, as shown in FIG. 7, lead 106 may include firstset 108 of fixation elements separated from second set 110 of fixationelements by electrodes 28. First and second sets 108 and 110 of fixationelements are each disposed along first outer surface portion 49A of leadbody 48. In the embodiment of lead 106 shown in FIG. 7, first and secondsets 108 and 110 of fixation elements, which may each include anysuitable number of fixation elements, may be located proximate anddistally, respectively, with respect to electrodes 28. While both leads14 (FIGS. 3A-3) and 106 include fixation elements for fixing leads 14and 106, respectively, to target stimulation site 18 (FIG. 1), which maybe within subcutaneous tissue 66 (FIG. 3A), lead 106 may be useful forlocally fixing distal end 48B of lead body 48. In some applications oftherapy system 10 (FIGS. 1 and 2), such as when therapy system 10 isused to stimulate a pudendal nerve, it may be desirable to locally fixdistal end 48B of lead body 48.

FIG. 8 is a perspective view of yet another embodiment of lead 112 inaccordance with the invention. In addition to first and second sets 108and 110 of fixation elements along first outer surface portion 49A oflead body 48, lead 112 includes third set 114 of fixation elementsbetween electrodes 28B and 28C. Third set 114 includes fixation elements116, 118, 120, and 122. In other embodiments, lead 112 may include a setof fixation elements between all of electrodes 28 or between any othercombination of electrodes (e.g., between electrodes 28A and 28B).

While each of leads 14, 82, 90, and 106 of FIGS. 3A, 5A, 6A, and 7include fixation elements angled toward proximal end 48A of lead body48, in other embodiments, the fixation elements may also be angledtoward distal end 48B of lead body 48. For example, fixation elements116 and 122 of third set 114 of fixation elements of lead 112 shown inFIG. 8 are angled toward proximal end 48A of lead body 48, whilefixation elements 118 and 120 are angled toward distal end 48B.

Fixation elements 116, 118, 120, and 122 each extend from lead body 48at an acute angle with respect to first portion 49A of lead body 48. Aspreviously discussed, fixation elements of a lead in accordance with theinvention may also extend radially outward at about 90° with respect tofirst portion 49A of lead body 48. An embodiment of such a lead is shownin FIG. 9, which is a perspective view of lead 124 including fixationelements 126, 128, and 130 that extend radially outward at approximately90° with respect to first outer surface portion 49A of lead body 48.

While tine-shaped fixation elements are shown in FIGS. 2-9 above, afixation element may have any suitable shape. FIGS. 10A and 10B are aperspective view and cross-sectional view, respectively, of lead 134,which includes fixation element 136 that extends around first outersurface portion 49A of lead body 48. Although fixation element 136 isshown in FIGS. 10A and 10B as expanding radially outward without anangular component (i.e. at 90° with respect to first outer surfaceportion 49A), in alternate embodiments, fixation element 136 may extendfrom lead body 48 at an angle with respect to first portion 49A.

As shown in FIGS. 10A and 10B, a single fixation element 136 is disposedbetween electrodes 28 and proximal end 48A of lead body 48. In alternateembodiments, lead 134 may include any suitable number of fixationelements that extend around first outer surface portion 49A of lead body48 and/or fixation element 134 may be used in combination with tine-likeor other fixation members that do not extend around first outer surfaceportion 49A of lead body 48. For example, in another embodiment,fixation member 136 may extend around 25%, 50% or 75% of the outerperimeter of first outer surface portion 49A of lead body 48. Forexample, FIG. 11 shows a schematic cross-sectional view of lead 138,which includes fixation element 140 extending around about 75% of firstouter surface portion 49A of lead body 48.

In each of leads 14, 82, 90, 106, 112, 124, 134 of FIGS. 3A, 5A, 6A,7-9, respectively, lead body 48 is cylindrical and defines first outersurface portion 49A carrying fixation elements, while second outersurface portion 49B is devoid of any fixation elements or includes oneor more fixation elements that do not engage with epidermis 62 (FIG. 3A)when lead 14 is implanted in subcutaneous tissue 66. In anotherembodiment, a lead may include a paddle shape (i.e. a paddle lead) andmay include fixation elements along one surface of the paddle lead, tothereby define a paddle lead including interior fixation when the paddlelead is implanted in subcutaneous tissue 66 (FIG. 2) of patient 20 ornear occipital region 29 (FIG. 1) of patient 20.

FIGS. 12A and 12B are a side view and a schematic cross-sectional viewof paddle lead 142, respectively, which includes substantially flat,paddle-like shaped lead body 144 coupled to distal end 146A of lead bodyconnector 146. A proximal end (not shown in FIG. 12A) of lead bodyconnector 146 may be mechanically coupled to a neurostimulator (e.g.,neurostimulator 12 of FIGS. 1 and 2) or another medical device. Leadbody 144 defines a “paddle” like shape, including first surface 144A andsecond surface 144B, which is opposite first surface 144A. As shown inFIG. 12B, which is a schematic cross-sectional view of lead body 144taken along line 12B-12B in FIG. 12A, lead body 144 defines an outerperimeter 145 (shown in phantom lines). Line 147 demarcates first andsecond surfaces 144A and 144B, respectively, which each extend aroundabout fifty percent of outer perimeter 145 of lead body 144.

In the embodiment shown in FIG. 12A, electrodes 148 are carried by firstsurface 144A of lead body 144. In another embodiment, paddle lead 142may also include electrodes along second surface 144B of lead body 144.Each of electrodes 148 may be electrically coupled to theneurostimulator, lead extension or other medical device via electricalconductors disposed within lead body connector 146. A proximal end (notshown in FIG. 12A) of lead body connector 146 may include electricalcontacts for electrically connecting the electrical conductors withinlead body connector 146 with the neurostimulator.

First surface 144A of lead body 144 includes fixation elements 149A-E,while second surface 144B is devoid of any fixation elements. In theembodiment shown in FIG. 12A, fixation elements 149A-D are tine-likestructures that are angled toward lead body connector 146. In otherembodiments, fixation elements 149A-D on first surface 144A of paddlelead body 144 may be any suitable shape or type of fixation element, andmay extend from first surface 144A at any suitable angle (e.g., radiallyoutward or away from lead body connector 146).

When paddle lead 142 is implanted in patient 20, lead 142 may beoriented such that first surface 144A, and accordingly fixation elements149A-D, faces away from epidermis 62, scalp 30 or another integumentarylayer of patient 20 in order to help minimize or eliminate anydiscomfort or irritation to patient attributable to fixation elements149A-D. Second surface 144B of lead body 144 provides a relativelysmooth surface for interfacing with epidermis 62 (FIG. 2) or scalp 30 ofpatient 20 because second surface 144B does not have any fixationelements that may engage with epidermis 62 or scalp 30 to create pointsof stress.

FIG. 13A is a side view of another embodiment of paddle lead 150, whichincludes substantially flat, paddle-like shaped lead body 144 coupled todistal end 146A of lead body connector 146 and electrodes on firstsurface 144A of lead body 144. In addition to fixation elements 149A-Don first surface 144A of lead body 144, lead 150 includes fixationelement 152 on second surface 144B of lead body 144. In particular,fixation element 152 is a layer of surgical adhesive that helps preventmigration of lead 150 following implantation in patient 20.Alternatively, surgical adhesive layer 152 may be adhesive elementsdisposed on or embedded with second surface 144B of lead body, asdiscussed by commonly assigned U.S. Patent Application Publication No.2008/0103579 by Martin T. Gerber, entitled “IMPLANTABLE MEDICALELONGATED MEMBER WITH ADHESIVE ELEMENTS” and filed on the same date asthe present disclosure, which is hereby incorporated by reference in itsentirety.

FIG. 13B is a side view of another embodiment of paddle lead 154, whichincludes fixation elements 156A-D along second surface 144B of lead body144. Fixation elements 149A-D as well as fixation elements 156A-D mayengage with surrounding tissue to help substantially fix a position oflead 154 proximate to target stimulation site 18. In the embodimentshown in FIG. 13B, fixation elements 156A-D are tine-like structuresthat are angled toward lead body connector 146. In other embodiments,fixation elements 156A-D on second surface 144B of paddle lead body 144may be any suitable shape or type of fixation element (e.g., one or moreballoon fixation elements) and may extend from second surface 144B atany suitable angle (e.g., radially outward or away from lead bodyconnector 146).

Fixation elements 156A-D do not extend from second surface 144B of leadbody 144 to the extent that fixation elements 149A-D extend from firstsurface 144A of lead body 144. That is, in FIG. 13A, dimension E, whichis the overall distance each of fixation elements 149A-D extend fromfirst surface 144A of lead body 144 is greater than dimension F, whichis the overall distance each of fixation elements 156A-D extend fromsecond surface 144B. Dimension F is selected such that fixation elements156A-D do not engage with and protrude into an integumentary layer(e.g., epidermis layer 62 (and in some cases, dermis layer 64) or scalp30 (FIG. 1)) of patient 20 when lead 154 is implanted in patient 20 suchthat first surface 144A of lead body 144 faces away from theintegumentary layer. The selective sizing of fixation elements 156A-Dmay thus help minimize any discomfort to patient 20 that is attributableto fixation elements 156A-D.

FIG. 14 is a flow diagram of process 160 for implanting a lead 14 (FIGS.1-3B) including fixation elements along first surface 49A of lead body48 in accordance with the invention. While lead 14 is referenced in thedescription of FIG. 14, it should be understood that process 160 may beused to implant any of leads 82, 90, 106, 112, 124, 134, and 138 ofFIGS. 5A, 6A, 7, 8, 9, 10A, and 11, respectively, or any other leadincluding fixation elements disposed along a portion (e.g., firstportion 49A) of an outer surface of lead body 48 in accordance with theinvention. Furthermore, while implantation of lead 14 into subcutaneoustissue 66 (FIG. 3A) of patient 20 is described, in other embodiments,lead 14 may be implanted proximate to any suitable target therapydelivery site in patient 20.

A lead introducer, such as an introducer needle, is introduced intoepidermis layer 62 (FIG. 3A) of patient 20 (FIG. 1) and a distal end ofthe introducer is guided into subcutaneous tissue 66 proximate to nerve68 (162). The introducer needle may be inserted into the patientpercutaneously or via an incision (e.g., incision 33 in FIG. 1) inepidermis layer 62. Lead 14 is introduced into a lumen of the introducer(164). In particular, distal end 14B of lead 14 is introduced into thelumen before proximal end 14A.

Lead 14 is advanced through the lumen until electrodes 28 adjacent todistal end 48B of lead body 48B of lead 14 are positioned proximate tonerve 68 (166). For example, distal end 14B of lead 14 may be advancedthrough the lumen of the introducer until at least distal end 14Bprotrudes past the lumen and into tissue of patient 20 and fixationelements 50, 52, and 54 are deployed from the introducer (i.e., areadvanced past a distal end of the introducer). Alternatively, fixationelements 50, 52, and 54 may be deployed from the introducer bywithdrawing the introducer or another sheath separating fixationelements 50, 52, and 54 from tissue of patient 20, thereby exposing lead14.

If necessary, lead 14 is oriented (e.g., rotated) such that first outersurface portion 49A of lead body 48 faces away from epidermis layer 62(168). Lead 14 may be oriented prior to or subsequent to positioningelectrodes 28 proximate to nerve 68 (166). Positioning of the introducerand/or orientation and positioning of lead 14 may be aided by imagingtechniques, such as by fluoroscopy using markers (e.g. radio-opaque orotherwise visible) on lead body 48. The markers may help indicate alocation of fixation elements 50, 52, and 54 with respect to theintroducer needle. Alternatively, lead 14 may be oriented using visiblemarker 65 (FIG. 2) and/or a stylet or introducer 16 may include features(e.g., channels for receiving fixation elements 50, 52, and 54) fororienting lead 14 such that first outer surface portion 49A of lead body48 faces away from epidermis 62 when lead 14 is implanted in patient 20.

Upon deployment into body tissue, fixation elements 50, 52, and 54engage with surrounding subcutaneous tissue 66 to substantially fixelectrodes 28 within subcutaneous tissue 66 proximate to nerve 68. Afterlead 14 is positioned, the lead introducer is withdrawn from patient 20(170). If an adhesive is also used to help prevent migration of lead 14after implantation in patient 20 (e.g., an adhesive disposed alongsecond outer surface portion 49B of lead body 48), the adhesive maybegin reacting with surrounding tissue or otherwise activating upondeployment into body tissue.

A lead including a vacuum cavity for receiving tissue may be useful forvarious electrical stimulation systems. For example, the lead may beused to deliver electrical stimulation therapy to patients to treat avariety of symptoms or conditions such as chronic pain, tremor,Parkinson's disease, multiple sclerosis, spinal cord injury, cerebralpalsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy,pelvic floor disorders, gastroparesis, muscle stimulation (e.g.,functional electrical stimulation (FES) of muscles) or obesity.

In addition, the fixation element arrangement described herein withrespect to leads 14, 82, 90, 106, 112, 124, 134, and 138 may also beuseful for fixing a catheter, such as a drug deliver catheter, proximateto a target drug delivery site.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

The invention claimed is:
 1. An apparatus comprising: an implantablemedical elongated member configured to couple to a medical device todeliver a therapy from the medical device to a target therapy deliverysite in a patient, the elongated member extending between a proximal endand a distal end and defining an outer surface extending between theproximal end and the distal end, the outer surface comprising: a firstouter surface portion, and a second outer surface portion extendingaround at least ten percent of an outer perimeter of the elongatedmember, wherein the second outer surface portion is at least partiallyaxially aligned with the first outer surface portion, and the elongatedmember comprises a plurality of stimulation electrodes positioned alongthe outer surface; a first fixation element extending a first distancefrom the first outer surface portion of the implantable medicalelongated member, wherein a longitudinally-extending section of thesecond outer surface portion proximate to the distal end of theelongated member and extending around at least ten percent of the outerperimeter of the elongated member is substantially devoid of anyfixation elements that extend the first distance from the second outersurface portion; and a second fixation element extending a seconddistance from the second outer surface portion of the implantablemedical elongated member, wherein the first distance is greater than thesecond distance, wherein the elongated member has a circularcross-section defining a first quadrant of the outer surface, a secondquadrant of the outer surface, a third quadrant of the outer surface,and a fourth quadrant of the outer surface, and the first fixationelement extends from at least one of the first, second or thirdquadrants, and the fourth quadrant of the outer surface is devoid of anyfixation elements that extend the first distance from the outer surface.2. The apparatus of claim 1, further comprising an exposed adhesivefixation element along at least a part of the second outer surfaceportion of the implantable medical elongated member.
 3. The apparatus ofclaim 1, wherein the first and second outer surface portions havesubstantially equal sizes.
 4. The apparatus of claim 1, wherein thesecond fixation element distance extends from the fourth quadrant of theouter surface of the implantable medical elongated member.
 5. Theapparatus of claim 4, wherein the first and second fixation elementsradially extend from the outer surface of the elongated member insubstantially opposite directions.
 6. The apparatus of claim 4, furthercomprising a third fixation element and a fourth fixation element,wherein the second fixation element extends from the second quadrant,the third fixation element extends from the third quadrant, and thefourth fixation element extends from the fourth quadrant.
 7. Theapparatus of claim 1, wherein the second outer surface portion extendsaround at least twenty-five percent of the outer perimeter of theelongated member.
 8. The apparatus of claim 1, wherein the firstfixation element comprises at least one of a tine, a flange, a balloonor a wire-like element.
 9. The apparatus of claim 1, wherein theelongated member comprises a lead comprising a lead body extendingbetween the proximal end and the distal end and the plurality ofstimulation electrodes are disposed on the lead body proximate to thedistal end of the lead body.
 10. The apparatus of claim 9, wherein thefirst fixation element is located between at least one of the electrodesof the plurality of stimulation electrodes and the proximal end of thelead body and the apparatus further comprises a third fixation elementlocated between the at least one of the electrodes of the plurality ofstimulation electrodes and the distal end of the lead body.
 11. Theapparatus of claim 9, wherein the first fixation element is disposedbetween at least two electrodes of the plurality of stimulationelectrodes.
 12. The apparatus of claim 9, wherein thelongitudinally-extending section of the second outer surface portionextends from the distal end of the elongated member to a proximal sideof the plurality of stimulation electrodes.
 13. The apparatus of claim1, wherein the elongated member comprises a catheter including an innerlumen to deliver a fluid from the medical device to the target therapydelivery site.
 14. The apparatus of claim 1, further comprising avisible marker on the elongated member to orient the elongated memberwith respect to an epidermis of the patient or an introducer.
 15. Asystem comprising: a medical device; an implantable medical elongatedmember configured to couple to the medical device to deliver a therapyfrom the medical device to a target therapy delivery site in a patient,the elongated member extending between a proximal end and a distal endand defining an outer surface extending between the proximal end and thedistal end, the outer surface comprising: a first outer surface portion,and a second outer surface portion extending around at least ten percentof an outer perimeter of the elongated member, wherein the second outersurface portion is at least partially axially aligned with the firstouter surface portion; and a first fixation element extending a firstdistance from the first outer surface portion of the implantable medicalelongated member, wherein a longitudinally-extending section of thesecond outer surface portion proximate to the distal end of theelongated member and extending around at least ten percent of the outerperimeter of the elongated member is devoid of any fixation elementsthat extend the first distance from second outer surface portion; and asecond fixation element extending a second distance from the secondouter surface portion of the implantable medical elongated member,wherein the first distance is greater than the second distance, whereinthe elongated member has a circular cross-section defining a firstquadrant of the outer surface, a second quadrant of the outer surface, athird quadrant of the outer surface, and a fourth quadrant of the outersurface, and the first fixation element extends from at least one of thefirst, second or third quadrants, and the fourth quadrant of the outersurface is devoid of any fixation elements that extend the firstdistance from the outer surface.
 16. The system of claim 15, furthercomprising an exposed adhesive fixation element along at least a part ofthe second outer surface portion of the implantable medical elongatedmember.
 17. The system of claim 15, wherein the elongated membercomprises at least one of a lead comprising a lead body extendingbetween a proximal end and a distal end and an electrode disposed on thelead body proximate to the distal end of the lead body or a catheter.18. The system of claim 17, wherein the elongated member is a lead, andthe longitudinally-extending section of the second outer surface portionextends from the distal end of the elongated member to a proximal sideof the electrode.
 19. The system of claim 15, wherein the medical devicecomprises at least one of a neurostimulator, a sensor or a fluiddelivery device.
 20. The system of claim 15, further comprising anintroducer configured to receive the elongated member, wherein theintroducer defines an inner lumen defining a channel configured toreceive the first fixation element.
 21. The system of claim 20, whereinthe elongated member comprises a first marker and the introducercomprises a second marker, and when the first and second markers arealigned, the first fixation element is aligned with the channel definedby the inner lumen of the introducer.
 22. The system of claim 20,wherein the first fixation element comprises a plurality of fixationelements and the channel defined by the inner lumen of the introducercomprises a plurality of channels.
 23. An implantable medical leadcomprising: a lead body defining a longitudinal outer surface, the leadbody comprising a circular cross-section defining a first quadrant ofthe longitudinal outer surface, a second quadrant of the longitudinalouter surface, a third quadrant of the longitudinal outer surface, and afourth quadrant of the longitudinal outer surface; at least twostimulation electrodes on the outer surface of the lead body; one ormore fixation elements extending a first distance format least one ofthe first, second or third quadrants of the longitudinal outer surfacean outer surface of the lead body, wherein the fourth quadrant of theouter surface is devoid of any fixation elements that extend the firstdistance from the outer surface; and one or more fixation elementsextending a second distance from the outer surface portion, wherein thefirst distance is greater than the second distance, wherein at least acircumferential sub-section of the outer surface extending over at leastten degrees is substantially devoid of the one or more fixation elementsextending the first distance from the outer surface portion, and whereinthe at least two stimulation electrodes and the one or more fixationelements extending the first distance from the outer surface portion arepositioned on a same side of the outer surface of the lead body.
 24. Theimplantable medical lead of claim 23, further comprising an exposedadhesive fixation element along the circumferential sub-section of theouter surface of the lead body.
 25. A method for implanting an elongatedmember in a patient, the method comprising: introducing the elongatedmember into the patient, the elongated member extending between aproximal end and a distal end and defining an outer surface comprising afirst outer surface portion and a second outer surface portion extendingaround at least ten percent of an outer perimeter of the elongatedmember, wherein the second outer surface portion is at least partiallyaxially aligned with the first outer surface portion, the elongatedmember further comprising: a first fixation element extending a firstdistance from the first outer surface portion of the implantable medicalelongated member, wherein a longitudinally-extending section of thesecond outer surface portion proximate to the distal end of theelongated member and extending around at least ten percent of the outerperimeter of the elongated member is substantially devoid of anyfixation elements that extend the first distance from second outersurface portion, and a second fixation element extending a seconddistance from the second outer surface portion of the implantablemedical elongated member, wherein the first distance is greater than thesecond distance; orienting the elongated member so that the second outersurface portion faces a superficial direction; and advancing theelongated member to a target therapy delivery site to deploy the firstfixation element into tissue of the patient, wherein the first fixationelement engages with surrounding tissue to substantially fix a positionof the elongated member proximate to the target therapy delivery site.26. The method of claim 25, wherein introducing the elongated memberinto the patient comprises introducing an introducer into the patient.27. The method of claim 26, wherein introducing the introducer into thepatient comprises introducing the introducer proximate to a peripheralnerve of the patient.
 28. The method of claim 26, further comprisingaligning a visible marker of the introducer with respect to an epidermisof the patient.
 29. The method of claim 26, further comprisingintroducing the elongated member into the introducer by aligning thefirst fixation element with a channel defined by an inner lumen of theintroducer.
 30. The method of claim 25, wherein upon orienting theelongated member so that the second outer surface portion faces thesuperficial direction, the first fixation element faces at least one ofaway from an epidermis of the patient or generally parallel to theepidermis of the patient.
 31. The method of claim 25, wherein the secondouter surface portion of the elongated member extends around at leasttwenty-five percent of the outer perimeter of the elongated member. 32.The method of claim 25, wherein the elongated member comprises at leastone of a lead comprising an electrode or a catheter.
 33. The method ofclaim 25, further comprising coupling the elongated member to a medicaldevice, the medical device delivering a therapy to the target therapydeliver site via the elongated member.
 34. The method of claim 33,wherein the medical device comprises at least one of a neurostimulator,fluid delivery device or sensor.